Dr. Dale Durran, University of Washington – Humidity and Cold Drinks

In today’s Academic Minute, Dr. Dale Durran of the University of Washington explains why it’s more difficult to keep your drink cold on a humid day.

Audio Pending...

Dale Durran is a professor of atmospheric sciences and an adjunct professor of applied mathematics at the University of Washington. His research interests include mesoscale dynamic meteorology, numerical methods, mountain meteorology, and atmospheric waves. His work has been published in a number of peer-reviewed journals and he holds a Ph.D. from the Massachusetts Institute of Technology.

In spring our skies are filled with puffy cumulus clouds, whose turrets grow upward because, like hot air balloons, they are warmer and less dense than the surrounding air. But, unlike hot-air balloons, the warmth inside cumulus clouds is not produced by burning propane; instead the heating inside a rising turret is produced by water vapor condensing to form cloud droplets.

We experience the reverse process, evaporative cooling, when our bodies give up the heat required to evaporate sweat from our skin. But we have very little intuition about the power of condensational heating. To improve your intuition, and to better understand cumulus clouds, consider a 12-oz can of cold beer. Suppose the can has become covered with a uniform layer of condensation having the thickness of a human hair. If all the heat released by this condensation is transferred to the beer, how much does the beer warm? A straightforward theoretical calculation gives the answer: nine degrees Fahrenheit!

How does this actually apply to your canned beverage? To find out, Professor Dargan Frierson and I measured the rate at which aluminum cans filled with 12 ounces of ice-cold water warmed inside an environmental chamber as we varied the air temperature and the humidity. It turns out, the rate of condensational heating is indeed significant on hot humid days. On a day when the temperature is87 degrees Fahrenheit and the relative humidity 70%, the condensation that forms over five minutes will heat the can’s contents by 10 degrees, and this condensational heating will exceed the dry heat transfer from the surrounding air. World-record humidities are observed near the Persian Gulf, and under those conditions, the five-minute condensational heating increases to 16 degrees. When your beer is warming on a hot muggy day, it’s not just the heat, its the humidity.

Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.

Related Content

In today’s Academic Minute, Michael Levin of Tufts University explains the process that determines organ placement as an embryo develops.

Michael Levin is Professor and Director of the Tufts Center for Regenerative and Developmental Biology at Tufts University. His research is focused on understanding morphological and behavioral information processing in living systems. He holds a Ph.D. in genetics from Harvard Medical School.

In today’s Academic Minute, Dr. Judith Ochrietor of the University of North Florida explains how a dangerous protein can also be dangerous for cancer.

Judith Ochrietor is an associate professor of biology at the University of North Florida where she uses her studies of cell adhesion and metabolism in the neural retina to train undergraduate and Masters of Science students. She earned a Ph.D. in Biochemistry from Ohio State University and later studied the development of the mammalian neural retina as a post-doctoral fellow at the University of Florida.